Actually, Extruded Polystyrene is referred to as XPS or Styrofoam. EPS is Expanded Polystyrene. The Pink...is that the Ownes Corning insulation? That is XPS. Also, you've been cautioned about the delam issue with XPS?
Regarless both XPS and EPS will disvolve when exposed to the styrenes in rattle can paint, so if you want to paint the foam, you'll use a water based paint like we used in kindergarten!
I believe that Tempera Poster Paint is available at most arts and crafts stores and works well.
Alternatively, you can paint after glassing and then shoot some clear acrylic over it to protect the artwork. You can use just about any type of paint over cured epoxy.
Keep us posted on the progress!